ISSN:
1573-9325
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Conclusions 1. The mechanism of failure of commercial iron is determined by the temperature-force conditions used in testing. At normal temperatures the metal fails by slip without any crack formation, irrespective of the stress conditions: at low temperatures failure is preceded by the development of trans-and intercrystalline microcracks, the space orientation of which depends on the form of the stress state. 2. The statistical distributions of the number and total length of isolated microcracks with respect to their orientation have been constructed from data obtained by the metallographic examination of ruptured specimens. The results show that the orientation of the majority of the microcracks formed in the initial stages of plastic flow is similar to that of the planes on which the maximum tensile stresses act, although microcracks having a substantially different orientation have also been observed. 3. Microcracks do not grow in a straight line within a single grain, but appear as a zigzag line. The distribution of the number and total length of the straight portions of the microcracks with respect to orientation indicates that the mean length of these portions is commensurate with the mean distance between the nonmetallic inclusions. The reason for the change in direction of the microcracks evidently lies in the interaction of the elastic-stress field at the tip of the crack with the elastic-stress field surrounding a nonmetallic inclusion. 4. At low temperatures the appearance of a second tensile stress has a significant effect, leading to a reduction in the ductility of the iron. The effect was most clearly observed at −100°C, at which temperature the maximum slip before failure in uniaxial tension considerably exceeded the maximum slip in biaxial tension. The suggestion is put forward that this effect is due to the smaller degree of opening of the nucleated microcracks in the presence of a second tensile stress.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01527676
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